I thought people on this site would like to read how you can build your own joule-thompson generator to make liquid nitrogen from air. The tutorial site is http://homemadeliquidnitrogen.com.
I made a pressure swing adsorber using an arduino-based controller for the solenoid valves. Using the PSA I get 98.5% pure N2 which I cool down in the my regeneration tower using a scuba compressor. I can produce about 350cc/hr of LN2.
The tutorial site has a link to a commercial-free video summarizing the whole process in 3 minutes.
Just thought you all might be interested.